Republican Senators are warning the White House that it will have a fight on its hands if the president chooses to nominate current U.S. Ambassador to the United Nations Susan Rice as his new Secretary of State.

Rice, a close Obama ally on foreign affairs since early in the 2008 campaign, is among the short list of names being circulated to succeed Hillary Rodham Clinton, who is planning to step down early in Obama’s next term. Republicans, however, are threatening to fight her nomination tooth and nail, citing questions that continue to swirl around the lethal attack on the U.S. consulate in Benghazi, Libya, and her role in the aftermath of that attack.

“I couldn’t support her,” one influential Republican Senator said prior to the election. And he predicted that several colleagues would “lay in the railroad tracks” to prevent her nomination.

Rice went on the Sunday news talk shows five days after the Sept. 11 assault — which killed U.S. Ambassador Christopher Stevens and three other Americans — claiming it appeared to have been a spontaneous response to an anti-Muslim video made in the United States. That later proved inaccurate, but the administration and fellow Democrats have pointed out that Rice’s comments were based on available intelligence assessments, which backed up her statements.

“If any administration official, including any career official, were on television on Sunday, Sept. 16, they would have said what Ambassador Rice said,” Undersecretary of State Patrick Kennedy testified at an Oct. 10 House Oversight and Government Reform hearing on the attack. “The information she had at that point from the intelligence community is the same that I had at that point.”

Republicans have dismissed that, maintaining that her assessment was part of the Obama administration’s political spin playing down the terrorist origins of the attack and thus raises questions about her judgment.

“Either she’s that naïve to be used in that way,” said the Senator, who was not yet prepared to speak publicly on Rice’s qualification, or “she totally misled the public.”

It also plays into worries Republicans have voiced that her loyalty to the president means she wouldn’t be a sufficiently independent voice at Foggy Bottom.

GOP Senators also remain immensely frustrated with the State Department’s handling of the Libya affair and the agency’s resistance to sharing information with Capitol Hill, according to a Republican Senate staffer. The State Department has been hesitant about releasing information while an independent review it authorized is under way, though it has started releasing some documents and will brief the Senate Foreign Relations Committee next week.

Rice’s nomination, the aide said this week, would give Republicans an opportunity to retaliate for the administration stonewalling.

“If they were to trot out Rice’s nomination, Republicans are pissed enough right now, they may take her as a scalp,” said the aide, whose boss sits on a committee investigating the Benghazi attacks.

It all adds up to a highly combustible confirmation fight that the White House may prefer to avoid.

In contrast, another top possibility for secretary of State — Senate Foreign Relations Chairman John Kerry, (D-Mass.) — would likely have a smooth path to confirmation.

While aides predict a number of Republicans would vote against him, he is also likely to win a smattering of GOP votes and not face the sort of blockade that Rice almost certainly would.